NEW ORLEANS — The now infamous blowout preventer from the doomed Gulf oil rig is in danger of corroding and its value as a key piece of evidence may be compromised, the owner of the rig alleges in a letter to federal investigators.

Philip Seymour Hoffman withdrew a total of $1,200 from an ATM at a supermarket near his New York City apartment the night before he was found lifeless in his bathroom with a syringe still in his left arm, sources told NBC News.

Transocean lawyer Steven Roberts said that "forensic testing has not yet begun" on the blowout preventer, or BOP, even though it has been sitting at a NASA facility in New Orleans for two months. "The testing facilities are not ready," he added, and "many of the critical preservation steps have not been completed."

"The critical BOP components have been subject to the elements, corrosion and deterioration such that the results of any eventual testing may now be compromised," Roberts wrote.

Investigators agreed to flush the control pods with fluid on Sept. 27 to prevent corrosion. But Roberts said in his letter that there have been no further preservation steps on the blowout preventer since then.

Transocean, along with BP and Halliburton, have been the focus of the investigation into the blowout, explosion and spill. But if evidence indicates the BOP failure was a key reason for the scale of the disaster it could shift some liability away from those companies to the BOP manufacturer, Cameron International.

The investigation team has previously asserted that it hadn't begun testing because of the time it was taking to develop procedures for the testing. Last month, a memo from the investigators to interested parties said final protocols would be submitted to the team for approval around Oct. 15.

The letter, sent on Nov. 3, was first obtained Wednesday by The Associated Press. Transocean on Wednesday told msnbc.com that it not heard back from the investigative team about its concerns.

Eileen Angelico, a spokeswoman for the investigation, declined to address the specific claims by Transocean. But she said investigators are "committed to preserving, securing and examining the evidence in accordance with standards developed in consultation with the Department of Justice and the Federal Bureau of Investigation to ensure that they will withstand the highest standard of judicial scrutiny."

The device failed to stop oil from gushing into the sea following the April 20 Deepwater Horizon explosion.

The blowout preventer, which Transocean was responsible for maintaining while it was being used on BP's well, was raised from the seafloor on Sept. 4. It was taken to the NASA facility a week later.

Roberts blasted the entire process used by investigators. "The plans for preserving the BOP were disrupted almost from the day the BOP stack was pulled to surface on September 4, 2010," he wrote.